Method for manufacturing liquid cooling jacket

ABSTRACT

Provided is a method for manufacturing a liquid cooling jacket including a jacket body and a sealing body joined to the jacket body. The method includes steps of: preparing; placing; first primary joining with a rotary tool; and second primary joining with the rotary tool. The rotary tool includes a base end pin and a distal end pin. The distal end pin includes a flat surface and a protrusion protruding from the flat surface. In the first primary joining and the second primary joining, friction stirring is performed in a state where the jacket body and the sealing body are brought in contact with the flat surface of the distal end pin and the base end pin and only the jacket body is brought in contact with a distal end surface of the protrusion.

TECHNICAL FIELD

The present invention relates to a method for manufacturing a liquidcooling jacket.

BACKGROUND ART

There has been a rotary tool, which includes a shoulder portion and astirring pin extending downward from the shoulder portion, used forfriction stir joining. The rotary tool is also used for manufacturing aliquid cooling jacket which includes a jacket body and a sealing body.The rotary tool is used for friction stir joining in a state where alower end surface of the shoulder portion presses metal members.Formation of burrs can be suppressed by the shoulder portion beingpressed against the metal members to press a plastically fluidizedmaterial. However, when a height position of joining is changed, defectsare liable to be formed, and the larger a recessed groove is, the moreburrs are generated.

Meanwhile, there has been a friction stir joining method with a rotarytool having a stirring pin to join two metal members, which includes aprimary joining step to perform friction stir joining in a state wherethe stirring pin being rotated is inserted into an abutted portion ofthe metal members and only the stirring pin is brought in contact withthe metal members (Patent Literature 1). According to the conventionaltechnology, a spiral groove is formed in an outer peripheral surface ofthe stirring pin. Friction stir joining is performed in a state where abase end portion is exposed while only the stirring pin is brought incontact with joined members. As a result, formation of defects issuppressed even when a height position of joining is changed, and a loadto a friction stirring apparatus is reduced. However, as a plasticallyfluidized material is not pressed by a shoulder portion, a recessedgroove formed in surfaces of the metal members tends to be larger and ajoined surface is made coarse. Further, bulged portions (portions, whichare bulged as compared to those before joining, of the front surfaces ofthe metal members) are formed on sides of the recessed groove.

Further, Patent Literature 2 describes a rotary tool having a shoulderportion and a stirring pin extending downward from the shoulder portion.Tapered surfaces are formed on outer peripheral surfaces of the shoulderportion and the stirring pin, respectively. A groove having a spiralshape in planar view is formed in the tapered surface of the shoulderportion. The groove has a semicircular shape in cross-sectional view.With the tapered surfaces, the metal members are stably joined even whenthicknesses of the metal members or a height position of joining ischanged. Still further, a plastically fluidized material flows into thegroove. A suitable plasticized region is formed by controlling the flowof the plastically fluidized material.

CITATION LIST Patent Literatures

Patent Literature 1: Japanese Patent Application Publication No.2013-39613

Patent Literature 2: Japanese Patent No. 4210148

SUMMARY OF THE INVENTION

Problems to be solved by the Invention

However, with the conventional technology described in Patent Literature2, the plastically fluidized material flows into the groove formed inthe tapered surface, to hinder the groove from functioning. Further,once the plastically fluidized material flows into the groove, the metalmembers are subjected to friction stir joining in a state where theplastically fluidized material is adhered to the groove. Therefore,there is a problem that the joined metal members are rubbed with theadhered material so that joining quality is deteriorated. Still further,the front surfaces of the joined metal members are made coarse, moreburrs are generated, and the recessed groove in the front surfaces ofthe metal members is formed larger.

From such a point of view, the present invention is intended to providea method for manufacturing a liquid cooling jacket having a smallerrecessed groove formed in front surfaces of metal members and having ajoined surface made less coarse.

Means to Solve the Problems

In order to solve such problems, the present invention provides a methodfor manufacturing a liquid cooling jacket, the liquid cooling jacketincluding a jacket body and a sealing body, the jacket body including abottom portion, a peripheral wall portion rising from a peripheral edgeof the bottom portion, and a columnar support rising from the bottomportion, the sealing body having a hole portion into which a distal endof the columnar support is inserted, and sealing an opening of thejacket body, the jacket body being joined to the sealing body byfriction stirring, the method including steps of: preparing for forminga peripheral wall stepped portion including a stepped bottom surface anda stepped side surface rising from the stepped bottom surface on aninner peripheral edge of the peripheral wall portion, forming a columnarsupport end surface of the columnar support so as to have the sameheight as a peripheral wall end surface of the peripheral wall portion,and forming a columnar support stepped portion including a steppedbottom surface and a stepped side surface rising from the stepped bottomsurface on an outer periphery of a distal end of the columnar support;placing the sealing body in the jacket body; first primary joining forperforming friction stirring to a first abutted portion, where thestepped side surface of the peripheral wall stepped portion is abuttedwith an outer peripheral side surface of the sealing body, with a rotarytool being moved around the first abutted portion by one lap; and secondprimary joining for performing friction stirring to a second abuttedportion, where the stepped side surface of the columnar support steppedportion is abutted with a hole wall of a hole portion, with a rotarytool being moved around the second abutted portion by one lap, whereinthe rotary tool is a primary joining rotary tool for friction stirringto include a base end pin and a distal end pin, wherein a taper angle ofthe base end pin is larger than a taper angle of the distal end pin, thebase end pin includes a pin stepped portion in a stepped shape formed onan outer peripheral surface thereof, and the distal end pin includes aflat surface perpendicular to a rotation axis of the rotary tool andincludes a protrusion protruding from the flat surface, and wherein, inthe first primary joining and the second primary joining, the frictionstirring is performed in a state where the jacket body and the sealingbody are brought in contact with the flat surface of the distal end pinand the base end pin, and only the jacket body is brought in contactwith a distal end surface of the protrusion.

Further, the present invention provides a method for manufacturing aliquid cooling jacket, the liquid cooling jacket including a jacket bodyand a sealing body, the jacket body including a bottom portion, aperipheral wall portion rising from a peripheral edge of the bottomportion, and a columnar support rising from the bottom portion, thesealing body sealing an opening of the jacket body, the jacket bodybeing joined to the sealing body by friction stirring, the methodincluding steps of: preparing for forming a peripheral wall steppedportion including a stepped bottom surface and a stepped side surfacerising from the stepped bottom surface on an inner peripheral edge ofthe peripheral wall portion, and forming a columnar support end surfaceof the columnar support so as to have the same height as the steppedbottom surface of the peripheral wall stepped portion; placing thesealing body in the jacket body; first primary joining of performingfriction stirring to a first abutted portion, where the stepped sidesurface of the peripheral wall stepped portion is abutted with an outerperipheral side surface of the sealing body, with a rotary tool beingmoved around the first abutted portion by one lap; and second primaryjoining of performing friction stirring to an overlapped portion, wherethe columnar support end surface of the columnar support is overlappedwith a rear surface of the sealing body, with a rotary tool being movedaround the overlapped portion, wherein the rotary tool is a primaryjoining rotary tool for friction stirring to include a base end pin anda distal end pin, wherein a taper angle of the base end pin is largerthan a taper angle of the distal end pin, the base end pin includes apin stepped portion in a stepped shape formed on an outer peripheralsurface thereof, and the distal end pin includes a flat surfaceperpendicular to a rotation axis of the rotary tool and includes aprotrusion protruding from the flat surface, and wherein, in the firstprimary joining, the friction stirring is performed in a state where thejacket body and the sealing body are brought in contact with the flatsurface of the distal end pin and the base end pin, and only the jacketbody is brought in contact with a distal end surface of the protrusion,and in the second primary joining, the friction stirring is performed ina state where the sealing body is brought in contact with the flatsurface of the distal end pin and the base end pin, and the jacket bodyis brought in contact with the distal end surface of the protrusion.

According to the joining method described above, the sealing body ispressed by the outer peripheral surface of the base end pin having alarge taper angle so that the recessed groove of the joined frontsurface is made small, and the bulged portions formed on sides of therecessed groove is not formed or made small. The stepped portion in astepped shape is shallow and has a wide exit angle so that theplastically fluidized material is hardly adhered to the outer peripheralsurface of the base end pin even when the plastically fluidized materialis pressed by the base end pin. Accordingly, the joined surface is madeless coarse and joining quality is suitably stabilized. Further, thedistal end pin is easily inserted to a deeper position. Still further,with the protrusion of the rotary tool, joining strength of the firstabutted portion, the second abutted portion, and the overlapped portionis further increased.

Further, in the preparing described above, the jacket body is preferablyformed by die-casting to have the bottom portion formed to be convextoward the front surface of the jacket body, and the sealing body ispreferably formed to be convex toward a front surface thereof.

There is a risk that heat input at the time of friction stir joiningcauses heat contraction in the plasticized regions and the sealing bodyof the liquid cooling jacket to be deformed in a concave shape. However,according to the manufacturing method, the jacket body and the sealingbody are formed in a convex shape in advance, and heat contraction isused to make the liquid cooling jacket flat.

Further, an amount of deformation of the jacket body is preferablymeasured in advance, and in the first primary joining and the secondprimary joining, the friction stirring is performed while an insertiondepth of the rotary tool is adjusted in accordance with the amount ofdeformation.

According to the manufacturing method, even when the jacket body and thesealing body are curved in a convex shape for friction stir joining, alength and a width of the plasticized region formed in the liquidcooling jacket are kept constant.

Further, in the first invention of the present application, the methodpreferably includes provisional joining of provisionally joining atleast either one of the first abutted portion and the second abuttedportion prior to the first primary joining and the second primaryjoining.

Still further, in the second invention of the present application, themethod preferably includes provisional joining of provisionally joiningthe first abutted portion prior to the first primary joining.

According to the manufacturing method, performing the provisionaljoining prevents the abutted portions from coming apart in the firstprimary joining and the second primary joining.

Further, in the first primary joining and the second primary joining, acooling plate, in which a cooling medium flows, is preferably arrangedto face a rear surface of the bottom portion, and the friction stirringis performed while the jacket body and the sealing body are cooled bythe cooling plate.

According to the manufacturing method, frictional heat is kept low sothat deformation of the liquid cooling jacket due to thermal contractionis reduced.

Further, a front surface of the cooling plate is preferably brought insurface-contact with a rear surface of the bottom portion. According tothe manufacturing method, cooling efficiency is improved.

Further, the cooling plate preferably has a cooling flow path in whichthe cooling medium flows, and the cooling flow path has a planar shapeto follow a moving trace of the rotary tool in the first primaryjoining.

According to the manufacturing method, a portion to be subjected tofriction stirring is intensively cooled, to more improve the coolingefficiency.

Further, the cooling flow path, in which the cooling medium flows, ispreferably formed of a cooling pipe embedded in the cooling plate.According to the manufacturing method, control of a cooling medium iseasily performed.

Further, in the first primary joining and the second primary joining, acooling medium preferably flows in a hollow portion defined by thejacket body and the sealing body, and friction stirring is performedwhile the jacket body and the sealing body are cooled.

According to the manufacturing method, frictional heat is kept low sothat deformation of the liquid cooling jacket due to thermal contractionis reduced. Further, according to the method, the jacket body is cooledby itself without using a cooling plate or the like.

Advantageous Effects of the Invention

According to the method for manufacturing a liquid cooling jacket of thepresent invention, the recessed groove formed in the front surfaces ofthe metal members is made smaller and the joined surface is made lesscoarse.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a primary joining rotary tool according to anembodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a joining mode of theprimary joining rotary tool.

FIG. 3 is an enlarged cross-sectional view of the primary joining rotarytool.

FIG. 4 is a side view of a provisional joining rotary tool according toan embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view of a joining mode of theprovisional joining rotary tool.

FIG. 6 is a perspective view of a liquid cooling jacket according to afirst embodiment of the present invention.

FIG. 7 is an exploded perspective view of the liquid cooling jacketaccording to the first embodiment of the present invention.

FIG. 8 is a cross-sectional view taken along a line I-I in FIG. 6.

FIG. 9 is a cross-sectional view of the liquid cooling jacket before aplacing step of a method for manufacturing the same according to thefirst embodiment.

FIG. 10 is a cross-sectional view of the liquid cooling jacket after theplacing step of the method for manufacturing the same according to thefirst embodiment.

FIG. 11 is a plan view of the liquid cooling jacket in a provisionaljoining step of the method for manufacturing the same according to thefirst embodiment.

FIG. 12 is a plan view of the liquid cooling jacket in a first primaryjoining step of the method for manufacturing the same according to thefirst embodiment.

FIG. 13 is a cross-sectional view of the liquid cooling jacket in thefirst primary joining step of the method for manufacturing the sameaccording to the first embodiment.

FIG. 14 is a plan view of the liquid cooling jacket in a second primaryjoining step of the method for manufacturing the same according to thefirst embodiment.

FIG. 15 is a cross-sectional view, taken along a line II-II in FIG. 14,of the liquid cooling jacket in the second primary joining step of themethod for manufacturing the same according to the first embodiment.

FIG. 16 is a cross-sectional view of the liquid cooling jacket in ahole-forming step of the method for manufacturing the same according tothe first embodiment.

FIG. 17 is a cross-sectional view of the liquid cooling jacket in amounting step of the method for manufacturing the same according to thefirst embodiment.

FIG. 18 is a conceptual view of a conventional rotary tool.

FIG. 19 is a conceptual view of the conventional rotary tool.

FIG. 20 is a perspective view of a liquid cooling jacket in a firstmodification of the method for manufacturing the same according to thefirst embodiment.

FIG. 21 is a perspective view of a table used in a second modificationof the method for manufacturing a liquid cooling jacket according to thefirst embodiment.

FIG. 22 is a perspective view of a jacket body and a sealing body beingfixed to the table in the second modification of the method formanufacturing a liquid cooling jacket according to the first embodiment.

FIG. 23 is an exploded perspective view of a liquid cooling jacket in athird modification of the method for manufacturing the same according tothe first embodiment.

FIG. 24 is a perspective view of a jacket body and a sealing body beingfixed to the table in the third modification of the method formanufacturing a liquid cooling jacket according to the first embodiment.

FIG. 25 is an exploded perspective view of a liquid cooling jacketaccording to a second embodiment.

FIG. 26 is a cross-sectional view of the liquid cooling jacket accordingto the second embodiment.

FIG. 27 is a cross-sectional view of the liquid cooling jacket before aplacing step of a method for manufacturing the same according to thesecond embodiment.

FIG. 28 is a cross-sectional view of the liquid cooling jacket after theplacing step of the method for manufacturing the same according to thesecond embodiment.

FIG. 29 is a plan view of the liquid cooling jacket in a provisionaljoining step of the method for manufacturing the same according to thesecond embodiment.

FIG. 30 is a plan view of the liquid cooling jacket in a first primaryjoining step of the method for manufacturing the same according to thesecond embodiment.

FIG. 31 is a cross-sectional view of the liquid cooling jacket in thefirst primary joining step of the method for manufacturing the sameaccording to the second embodiment shown in FIG. 30.

FIG. 32 is a plan view of the liquid cooling jacket in a second primaryjoining step of the method for manufacturing the same according to thesecond embodiment.

FIG. 33 is a cross-sectional view, taken along a line III-III in FIG.32, of the liquid cooling jacket in the second primary joining step ofthe method for manufacturing the same according to the secondembodiment.

FIG. 34 is a cross-sectional view of the liquid cooling jacket in ahole-forming step of the method for manufacturing the same according tothe second embodiment.

FIG. 35 is a cross-sectional view of the liquid cooling jacket in amounting step of the method for manufacturing the same according to thesecond embodiment.

FIG. 36 is a cross-sectional view of a first modification of the primaryjoining rotary tool.

FIG. 37 is a cross-sectional view of a second modification of theprimary joining rotary tool.

FIG. 38 is a cross-sectional view of a third modification of the primaryjoining rotary tool.

EMBODIMENTS OF THE INVENTION First Embodiment

A description is given of a liquid cooling jacket and a method formanufacturing a liquid cooling jacket according to a first embodiment ofthe present invention with reference to the accompanying drawings.First, a primary joining rotary tool and a provisional joining rotarytool used in the present embodiment are described.

As illustrated in FIG. 1, a primary joining rotary tool (rotary tool) Fis a tool used for friction stir joining. The primary joining rotarytool F is formed of tool steel, for example. The primary joining rotarytool F mainly includes a base shaft portion F1, a base end pin F2, and adistal end pin F3. A protrusion F5 is formed at a distal end of thedistal end pin F3.

The base shaft portion F1 is a portion which has a columnar shape and isconnected to a main shaft of a friction stirring apparatus. A rotationaxis of the primary joining rotary tool F may be inclined with respectto the vertical direction, but coincides with the vertical direction inthe present embodiment. Further, a surface perpendicular to the verticaldirection is defined as the horizontal plane.

The base end pin F2 is continuous to the base shaft portion F1 and istapered off toward the distal end thereof. The base end pin F2 has afrustoconical shape. A taper angle A1 of the base end pin F2 may be setas appropriate, and is set at an angle of 135° to 160°, for example.When the taper angle Al1is less than an angle of 135° or more than anangle of 160°, a joined surface after friction stirring is made coarse.The taper angle A1 is larger than a taper angle A2 of the distal end pinF3 to be described below. As illustrated in FIG. 3, a pin steppedportion 30 in a stepped shape is formed on an outer peripheral surfaceof the base end pin F2 over an entire height direction thereof. The pinstepped portion 30 is spirally formed clockwise or counterclockwise.That is, the pin stepped portion 30 has a spiral shape in planar viewand has a stepped shape in side view. In the present embodiment, therotary tool is rotated clockwise so that the pin stepped portion 30 isformed counterclockwise from the base end toward the distal end.

In a case where the primary joining rotary tool F is rotatedcounterclockwise, the pin stepped portion 30 is preferably formedclockwise from the base end toward the distal end. With the structure, aplastically fluidized material flows toward the distal end through thepin stepped portion 30 so that metal overflowing outside the joinedmetal members is reduced. The pin stepped portion 30 includes a steppedbottom surface 30 a and a stepped side surface 30 b. A distance Z1(horizontal distance) between adjacent ridges 30 c of the pin steppedportion 30 is appropriately set in association with a stepped angle C1to be described below and a height Y1 of the stepped side surface 30 bto be described below.

The height Y1 of the stepped side surface 30 b may be appropriately set,and is set to 0.1 mm to 0.4 mm, for example. When the height Y1 is lessthan 0.1 mm, the joined surface is made coarse. Meanwhile, when theheight Y1 exceeds 0.4 mm, the joined surface is likely made coarse, andthe number of effective stepped portions (the number of pin steppedportions 30 being in contact with the joined metal members) is reduced.

The stepped angle Cl defined by the stepped bottom surface 30 a and thestepped side surface 30 b may be set as appropriate, and is set at anangle of 85 to 120°, for example. The stepped bottom surface 30 a is inparallel to the horizontal plane in the present embodiment. The steppedbottom surface 30 a may be inclined in a range of an angle of −5° to+15° with respect to the horizontal plane from the rotation axis of thetool toward the outer peripheral direction (“−” indicates downward withrespect to the horizontal plane, and “+” indicates upward with respectto the horizontal plane). The distance Z1, the height Y1 of the steppedside surface 30 b, the stepped angle C1, and the angle of the steppedbottom surface 30 a with respect to the horizontal plane are set asappropriate such that the plastically fluidized material flows outsidewithout accumulating and adhering inside the pin stepped portion 30, andthe joined surface is made less coarse by pressing the plasticallyfluidized material with the stepped bottom surface 30 a.

The distal end pin F3 is formed continuously to the base end pin F2. Thedistal end pin F3 has a frustoconical shape. The distal end of thedistal end pin F3 has a flat surface F4 which is flat. The taper angleA2 of the distal end pin F3 is smaller than the taper angle A1 of thebase end pin F2. A spiral groove 31 is formed in the outer peripheralsurface of the distal end pin F3. The spiral groove 31 may be formedclockwise or counterclockwise. In the present embodiment, the primaryjoining rotary tool F is rotated clockwise so that the spiral groove 31is engraved counterclockwise from the base end toward the distal end.

When the primary joining rotary tool F is rotated counterclockwise, thespiral groove 31 is preferably engraved clockwise from the base endtoward the distal end. With the structure, the plastically fluidizedmaterial flows toward the distal end through the spiral groove 31 sothat the metal overflowing outside the joined metal members is reduced.The spiral groove 31 includes a spiral bottom surface 31 a and a spiralside surface 31 b. A distance (horizontal distance) between adjacentridges 31 c of the spiral groove 31 is referred to as a distance Z2. Aheight of the spiral side surface 31 b is referred to as a height Y2. Aspiral angle C2 defined by the spiral bottom surface 31 a and the spiralside surface 31 b is set at an angle of 45° to 90°, for example. Thespiral groove 31 serves to increase frictional heat by coming in contactwith the joined metal members and to guide the plastically fluidizedmaterial toward the distal end.

As illustrated in FIG. 2, when friction stir joining is performed withthe primary joining rotary tool F, surfaces of the joined metal members(a jacket body or a sealing body 3 described below) are pressed by theouter peripheral surface of the base end pin F2 of the primary joiningrotary tool F for friction stir joining. An insertion depth of theprimary joining rotary tool F is set such that at least a portion of thebase end pin F2 comes in contact with the surfaces of the joined metalmembers. A plasticized region W1 (or plasticized regions W2) is formedof frictionally stirred metal being hardened in a moving trace of theprimary joining rotary tool F.

The flat surface F4 is a flat surface perpendicular to the rotationaxis. The protrusion F5 is formed at the center of the flat surface F4.A shape of the protrusion F5 is not particularly limited, and is acolumnar shape in the present embodiment.

As illustrated in FIG. 4, a provisional joining rotary tool G includes ashoulder portion G1 and a stirring pin G2. The provisional joiningrotary tool G is formed of tool steel, for example. As illustrated inFIG. 5, the shoulder portion G1 is a portion which is connected to themain shaft of the friction stirring apparatus and serves to press theplastically fluidized metal. The shoulder portion G1 has a columnarshape. The shoulder portion G1 has a lower end surface in a concaveshape to prevent the fluidized metal from flowing outside.

The stirring pin G2 extends downward from the shoulder portion G1 to becoaxial with the shoulder portion G1. The stirring pin G2 is tapered offwith the increasing distance from the shoulder portion G1. A spiralgroove G3 is engraved in an outer peripheral surface of the stirring pinG2.

As illustrated in FIG. 5, when friction stir joining is performed withthe provisional joining rotary tool G, the rotating stirring pin G2 andthe lower end surface of the shoulder portions G1 are inserted into andmoved in the joined metal members. A plasticized region W is formed offrictionally stirred metal being hardened in a moving trace of theprovisional joining rotary tool G.

Next, a description is given of a liquid cooling jacket of the presentembodiment. As illustrated in FIG. 6, a liquid cooling jacket 1according to the present embodiment includes a jacket body 2 and asealing body 3, and has a rectangular parallelepiped shape. The jacketbody 2 and the sealing body 3 are integrated by friction stir joining.The liquid cooling jacket 1 has a hollow portion inside and heattransfer fluid such as water is circulated therein. The heat transferfluid is circulated in the hollow portion so that the liquid coolingjacket 1 allows a heating element mounted thereon, for example, to becooled.

As illustrated in FIG. 7, the jacket body 2 is a box-shaped body whosetop is open. The jacket body 2 includes a bottom portion 10, aperipheral wall portion 11, and a plurality of columnar supports 12. Amaterial of the jacket body 2 is appropriately selected from frictionstirrable metal such as aluminum, an aluminum alloy, copper, a copperalloy, titanium, a titanium alloy, magnesium, and a magnesium alloy. Inthe present embodiment, the jacket body 2 is made of an aluminum alloywhich is the same material as the sealing body 3, but an aluminum alloycasting material (such as JIS AC4C, ADC12) may be used.

The bottom portion 10 has a rectangular plate shape in planar view. Theperipheral wall portion 11 stands on a peripheral edge of the bottomportion 10, and has a rectangular frame shape in planar view. Theperipheral wall portion 11 is formed of wall portions 11A, 11B, 11C, and11D, each having the same thickness. The wall portions 11A and 11B areshort side portions which face to each other. Further, the wall portions11C and 11D are long side portions which face to each other. A recessedportion 13 is defined inside the bottom portion 10 and the peripheralwall portion 11.

A peripheral wall stepped portion 14 is formed in a peripheral wall endsurface 11 a as an end surface of the peripheral wall portion 11 alongan inner peripheral edge of the peripheral wall portion 11 of the jacketbody 2. The peripheral wall stepped portion 14 is formed of a steppedbottom surface 14 a and a stepped side surface 14 b standing on thestepped bottom surface 14 . The stepped bottom surface 14 a is formed ata position one step lower than the peripheral wall end surface 11 a.

The columnar supports 12 are provided to stand on the bottom portion 10and has a columnar shape. The number of columnar supports 12 is notlimited as long as one or more columnar supports are arranged, and fourcolumnar supports are arranged in the present embodiment. The columnarsupports 12 each have the same shape. Each of the columnar supports 12has a large-diameter portion 15 and a small-diameter portion 16 formedso as to protrude at a distal end of the large-diameter portion 15. Boththe large-diameter portion 15 and the small-diameter portion 16 have acolumnar shape. A columnar support stepped portion 17 is formed on astep between the large-diameter portion 15 and the small-diameterportion 16.

The columnar support stepped portion 17 has a stepped bottom surface 17a and a stepped side surface 17 b rising from the stepped bottom surface17 a. A columnar support end surface 16 a is formed at an end surface ofthe small-diameter portion 16. The stepped bottom surface 17 a is formedto have the same height as the stepped bottom surface 14 a of theperipheral wall stepped portion 14. Further, the columnar support endsurface 16 a is formed to have the same height as the peripheral wallend surface 11 a.

The sealing body 3 is a rectangular plate-shaped member in planar viewto seal the opening of the jacket body 2. In the present embodiment, thesealing body 3 is made of an aluminum alloy which is the same materialas that of the jacket body 2, but an aluminum alloy malleable material(such as JIS A1050, A1100, and A6063) may be used. The sealing body 3 isformed to have a size to be placed in the peripheral wall steppedportion 14 without any gap. A thickness of the sealing body 3 isapproximately the same height of the stepped side surface 14 b. Thesealing body 3 has four hole portions 19 formed therein, whichcorrespond to the columnar supports 12. The hole portion 19 has acircular shape in planar view and the small-diameter portion 16 isinserted therein.

As illustrated in FIG. 8, the liquid cooling jacket 1 is formed of thejacket body 2 and the sealing body 3 being integrally joined together byfriction stirring. The liquid cooling jacket 1 is joined by frictionstirring, respectively, at a first abutted portion J1, where the steppedside surface 14 b of the peripheral wall stepped portion 14 is abuttedwith an outer peripheral side surface 3 c of the sealing body 3, and atfour second abutted portions J2, where the stepped side surfaces 17 b ofthe columnar support stepped portions 17 are abutted with the hole walls19 a of the hole portions 19. The plasticized region W1 is formed at thefirst abutted portion J1 and the plasticized region W2 is formed in thesecond abutted portions J2. The hollow portion, in which the heattransfer fluid circulates to transport heat outside, is formed insidethe liquid cooling jacket 1.

Next, a description is given of a method for manufacturing a liquidcooling jacket (a method for manufacturing a liquid cooling jackethaving a heating element) according to the first embodiment. The methodfor manufacturing a liquid cooling jacket includes a preparing step, aplacing step, a fixing step, a provisional joining step, a first primaryjoining step, a second primary joining step, a hole-forming step, a burrremoving step, and a mounting step.

As illustrated in FIG. 7, the preparing step is a step of forming thejacket body 2 and the sealing body 3. The jacket body 2 is formed bydie-casting, for example.

As illustrated in FIGS. 9 and 10, the placing step is a step of placingthe sealing body 3 in the jacket body 2 while the small-diameterportions 16 of the columnar supports 12 are inserted into the holeportions 19 of the sealing body 3. A rear surface 3 b of the sealingbody 3 is brought in surface-contact with the stepped bottom surface 14a of the peripheral wall stepped portion 14 and the stepped bottomsurfaces 17 a of the columnar support stepped portions 17, respectively.The placing step makes the stepped side surface 14 b of the steppedportion 14 abut with the outer peripheral side surface 3 c of thesealing body 3 to form the first abutted portion J1. The first abuttedportion J1 has a rectangular frame shape in planar view. Further, theplacing step makes the stepped side surfaces 17 b of the columnarsupport stepped portions 17 abut with the hole walls 19 a of the holeportions 19 to form the second abutted portions J2. The second abuttedportion J2 has a circular shape in planar view.

The jacket body 2 and the sealing body 3 are fixed to a table (notshown) in the fixing step. The jacket body 2 and the sealing body 3 areimmovably fixed to the table with fixing jigs such as clamps.

As illustrated in FIG. 11, the provisional joining step is a step ofprovisionally joining the jacket body 2 to the sealing body 3. In theprovisional joining step, friction stir joining is performed to thefirst abutted portion J1 with the provisional joining rotary tool G. Theplasticized region W is formed in the moving trace of the provisionaljoining rotary tool G. The provisional joining may be performedcontinuously or intermittently as illustrated in FIG. 11. Theprovisional joining rotary tool G is small so that thermal deformationof the jacket body 2 and the sealing body 3 in the provisional joiningis reduced.

As illustrated in FIGS. 12 and 13, the first primary joining step is astep of performing friction stir joining to the first abutted portion J1with the primary joining rotary tool F. In the first primary joiningstep, the primary joining rotary tool F, which is rotated clockwise, isinserted in a start position s1 formed at any position on the firstabutted portion J1, and is moved clockwise in the first abutted portionJ1. That is, the primary joining rotary tool F is moved around by onelap clockwise in a peripheral edge of the sealing body 3. Theplasticized region W1 is formed in the moving trace of the primaryjoining rotary tool F.

As illustrated in FIG. 13, in the first primary joining step, frictionstirring is performed in a state where the distal end pin F3 and thebase end pin F2 come in contact with the peripheral wall portion 11 ofthe jacket body 2 and the sealing body 3. In the first primary joiningstep, friction stir joining is performed while the peripheral wall endsurface 11 a of the peripheral wall portion 11 and the front surface 3 aof the sealing body 3 are pressed by the outer peripheral surface of thebase end pin F2 of the primary joining rotary tool F. The insertiondepth of the primary joining rotary tool F is set such that at least theplasticized region W1 reaches the stepped bottom surface 14 a and atleast a part of the base end pin F2 comes in contact with the peripheralwall end surface 11 a of the peripheral wall portion 11 and the frontsurface 3 a of the sealing body 3. In the present embodiment, theinsertion depth is set such that the distal end pin F3 comes in contactwith the sealing body 3 and the peripheral wall portion 11 and a distalend surface F6 of the protrusion F5 comes in contact with only theperipheral wall portion 11. That is, the insertion depth is set suchthat a side surface of the protrusion F5 is positioned in the steppedbottom surface 14 a. Then, the primary joining rotary tool F is moved ina state of having a constant height position to trace the first abuttedportion J1.

When the primary joining rotary tool F is moved clockwise around thesealing body 3 as in the present embodiment, the primary joining rotarytool F is preferably rotated clockwise. Meanwhile, when the primaryjoining rotary tool F is moved counterclockwise around the sealing body3, the primary joining rotary tool F is preferably rotatedcounterclockwise.

Joint defects may be generated on the left side in a traveling directionwhen the primary joining rotary tool F is rotated clockwise and on theright side in the traveling direction when the primary joining rotarytool F is rotated counterclockwise. When the joint defects are generatedin the thin sealing body 3, watertightness and airtightness may bedegraded. However, by setting the traveling direction and the rotatingdirection of the primary joining rotary tool F as described above, evenif joint defects are generated due to friction stir joining, the defectsare generated on the jacket body 2 side having a comparatively largethickness which is far away from the hollow portion of the liquidcooling jacket 1, so that the degradation in watertightness andairtightness is reduced.

As illustrated in FIG. 12, the primary joining rotary tool F is movedaround by one lap in the first abutted portion J1 and then is furthermoved to pass through the start position s1. Then, when reaching an endposition e1, the primary joining rotary tool F is moved upward so as tobe pulled out of the wall portion 11A.

If a pulled-out mark remains in the peripheral wall end surface 11 a ofthe wall portion 11A and the front surface 3 a of the sealing body 3after the primary joining rotary tool F is pulled out of the wallportion 11A, a repairing step of repairing the pulled-out mark may beperformed. In the repairing step, the pulled-out mark is repaired bybuild-up welding to fill welded metal in the pulled-out mark, forexample. Thus, the peripheral wall end surface 11 a and the frontsurface 3 a of the sealing body 3 are flattened.

When the primary joining rotary tool F is pulled out of the peripheralwall portion 11, the primary joining rotary tool F is gradually movedupward while being moved on the peripheral wall end surface 11 a of theperipheral wall portion 11, for example, so that the insertion depth ofthe primary joining rotary tool F is gradually shallower. Thus, apulled-out mark after the first primary joining step does not remain oris made smaller in the peripheral wall end surface 11 a and the frontsurface 3 a of the sealing body 3.

As illustrated in FIGS. 14 and 15, the second primary joining step is astep of performing friction stir joining to each second abutted portionJ2 with the primary joining rotary tool F. In the second primary joiningstep, the primary joining rotary tool F, which is rotated clockwise, isinserted into a start position s2 formed at any position on the secondabutted portion J2, and is moved counterclockwise in the second abuttedportion J2. The plasticized region W2 is formed in the second abuttedportion J2 through the second primary joining step.

As illustrated in FIG. 15, in the second primary joining step, frictionstirring is performed in a state where the distal end pin F3 and thebase end pin F2 come in contact with the columnar support 12 of thejacket body 2 and the sealing body 3. In the second primary joiningstep, friction stir joining is performed while the columnar support endsurface 16 a of the columnar support 12 and the front surface 3 a of thesealing body 3 are pressed by the outer peripheral surface of the baseend pin F2 of the primary joining rotary tool F. In the presentembodiment, the insertion depth is set such that a vicinity of thecenter in the height direction of the outer peripheral surface of thebase end pin F2 comes in contact with the columnar support end surface16 a of the columnar support 12 and the front surface 3 a of the sealingbody 3. Further, the insertion depth of the primary joining rotary toolF is set such that the distal end pin F3 comes in contact with both thecolumnar support 12 and the sealing body 3, and the distal end surfaceF6 of the protrusion F5 comes in contact with only the columnar support12. In other words, the insertion depth is set such that the sidesurface of the protrusion F5 positions in the stepped bottom surface 17a. Then, the primary joining rotary tool F is moved in a state of havinga constant height position to trace the second abutted portion J2.

The insertion depth of the primary joining rotary tool F is notnecessarily constant. The insertion depth may be changed for the firstprimary joining step and the second primary joining step.

In the second primary joining step, when the primary joining rotary toolF is moved counterclockwise with respect to the columnar support 12 asin the present embodiment, the primary joining rotary tool F ispreferably rotated clockwise. Meanwhile, when the primary joining rotarytool F is moved clockwise with respect to the columnar support 12, theprimary joining rotary tool F is preferably rotated counterclockwise. Bysetting the traveling direction and rotating direction of the primaryjoining rotary tool F as described above, even if joint defects aregenerated due to friction stir joining, the defects are generated on thecolumnar support 12 side having a relatively large thickness which isfar away from the hollow portion of the liquid cooling jacket 1, so thatthe degradation in watertightness and airtightness is reduced.

As illustrated in FIG. 14, the primary joining rotary tool F is movedaround by one lap in the second abutted portion J2 and then iscontinuously moved to pass through the start position s2. Then, theprimary joining rotary tool F is moved to the end position e2 set on thesecond abutted portion J2. When reaching the end position e2, theprimary joining rotary tool F is moved upward so as to be pulled out ofthe second abutted portion J2.

If a pulled-out mark remains in the second abutted portion J2 after theprimary joining rotary tool F is pulled out of the second abuttedportion J2, a repairing step of repairing the pulled-out mark may beperformed. In the repairing step, the pulled-out mark is repaired bybuild-up welding to fill welded metal in the pulled-out mark, forexample. Thus, the front surface 3 a of the sealing body 3 and thecolumnar support end surface 16 a of the columnar support 12 areflattened.

When the primary joining rotary tool F is pulled out of the secondabutted portion J2, the primary joining rotary tool F may be shiftedtoward the center of the columnar support 12 and then pulled out of thecolumnar support 12. Further, when the primary joining rotary tool F ispulled out of the second abutted portion J2, the primary joining rotarytool F may gradually be moved upward while being moved on the secondabutted portion J2 or the columnar support end surface 16 a, forexample, so that the insertion depth of the primary joining rotary toolF is gradually shallower. Thus, a pulled-out mark after the secondprimary joining step does not remain or is made smaller in the frontsurface 3 a of the sealing body 3 or the columnar support end surface 16a of the columnar support 12.

As illustrated in FIG. 16, the hole-forming step is a step of formingfixing holes X for mounting a heating element H on each columnar support12. The fixing holes X are each formed to penetrate a part of theplasticized region W2 so as to reach the columnar supports 12.

In the burr removing step, burrs, which are formed through the firstprimary joining step, the second primary joining step, and thehole-forming step, exposed on the front surfaces of the jacket body 2and the sealing body 3 are removed. With the step, the front surfaces ofthe jacket body 2 and the sealing body 3 are clearly finished.

As illustrated in FIG. 17, the mounting step is a step of mounting theheating element H with fitting members M. When the heating element H ismounted, through holes formed in a flange H1 of the heating element Hare communicated with the fixing holes X and the heating element H isfixed with the fitting members M such as screws. The fitting members Mare each inserted to a position reaching the columnar supports 12.

In the present embodiment, the fixing holes X are formed in the sealingbody 3 side to have the heating element H mounted thereon, but thefixing holes X reaching the columnar supports 12 may be formed in thebottom portion 10 to have the heating element H mounted thereon. Theheating element H merely needs to be mounted on at least one of thesealing body 3 and the bottom portion 10. Further, in the presentembodiment, the fixing holes X are formed, but the heating element H maybe fixed with the fitting members M without the fixing holes X beingformed.

Next, an advantageous effect of the present embodiment is described.

As illustrated in FIG. 18, a shoulder portion of a conventional primaryjoining rotary tool 100 does not press front surfaces of joined metalmembers 110 so that a recessed groove (a recessed groove defined byfront surfaces of the joined metal members and a front surface of aplasticized region) is made large and a joined surface is made coarse.Further, bulged portions (portions, which are bulged compared with thosebefore joining, of the front surfaces of the joined metal members) areformed on sides of the recessed groove. Meanwhile, as in a conventionalprimary joining rotary tool 101 as illustrated in FIG. 19, when a taperangle β of the primary joining rotary tool 101 is set to be larger thana taper angle α of the primary joining rotary tool 100, the primaryjoining rotary tool 101 presses the front surfaces of the joined metalmembers 110 more than the primary joining rotary tool 100 does, and therecessed groove is made small and the bulged portions also made small.However, downward plastic flow increases so that kissing bonds arelikely to be generated in a lower portion of a plasticized region.

In contrast, according to the method for manufacturing a liquid coolingjacket of the present embodiment, the primary joining rotary tool F hasa structure including the base end pin F2, and the distal end pin F3which has a smaller taper angle than the taper angle A1 of the base endpin F2. This facilitates insertion of the primary joining rotary tool Finto the jacket body 2 and the sealing body 3. Further, the taper angleA2 of the distal end pin F3 is small, to facilitate the insertion of theprimary joining rotary tool F into a deep position in the jacket body 2and the sealing body 3. Still further, the taper angle A2 of the distalend pin F3 is small so that the primary joining rotary tool F suppressesdownward plastic flow more than the primary joining rotary tool 101.This structure prevents kissing bonds from being generated in lowerportions of the plasticized regions W1 and W2. Meanwhile, the taperangle A1 of the base end pin F2 is large so that joining is stablyperformed, as compared with the conventional rotary tool, even ifthicknesses of the jacket body 2 and the sealing body 3 and a heightposition for joining are changed.

Further, the plastically fluidized material is pressed by the outerperipheral surface of the base end pin F2 so that the recessed grooveformed in the joined front surface is made small and the bulged portionsto be formed on the sides of the recessed groove are not formed or areformed smaller. Furthermore, the pin stepped portion 30 in a steppedshape is shallow and has a wide exit angle so that the plasticallyfluidized material easily flows outside the pin stepped portion 30 whilethe plastically fluidized material is pressed by the stepped bottomsurface 30 a. Therefore, the plastically fluidized material is hardlyadhered to the outer peripheral surface of the base end pin F2 even whenthe plastically fluidized material is pressed by the base end pin F2.Accordingly, the joined surface is made less coarse and joining qualityis suitably stabilized.

Further, the sealing body 3 is supported by the columnar supports 12,and the sealing body 3 and the columnar supports 12 are joined byfriction stir joining, to increase deformation resistance of the liquidcooling jacket 1. Still further, according to the present embodiment,the columnar supports 12 are arranged in the hollow portion of theliquid cooling jacket 1, to allow the heat transport fluid to come incontact with the outer peripheral surfaces of the columnar supports 12.Therefore, the heat transferred from the heating element H to thecolumnar supports 12 via the fitting members M is efficientlydischarged. That is, heat leakage through the fitting members M, withwhich the heating element H is fixed to the liquid cooling jacket 1, isprevented. Yet further, the columnar supports 12, to which the heatingelement H is fixed, are arranged inside the jacket body 2 so that theliquid cooling jacket 1 is reduced in size.

Further, in the first primary joining step, the insertion depth of theprimary joining rotary tool F is set such that the flat surface F4 ofthe distal end pin F3 comes in contact with both the peripheral wallportion 11 and the sealing body 3 and the distal end surface F6 of theprotrusion F5 comes in contact with only the peripheral wall portion 11.Metal around the protrusion F5 is brought upward by the protrusion F5and is pressed by the flat surface F4. Thus, a vicinity of theprotrusion F5 is frictionally stirred reliably, and oxide films of thefirst abutted portion J1 and of the overlapped surface between thestepped bottom surface 14 a and the rear surface 3 b of the sealing body3 are reliably shut off. Therefore, joining strength of the firstabutted portion J1 is further increased.

Further, in the second primary joining step, the insertion depth of theprimary joining rotary tool F is set such that the flat surface F4 ofthe distal end pin F3 comes in contact with both the columnar support 12and the sealing body 3 and the distal end surface F6 of the protrusionF5 comes in contact with only the columnar support 12. Metal around theprotrusion F5 is brought upward by the protrusion F5 and is pressed bythe flat surface F4. Thus, a vicinity of the protrusion F5 isfrictionally stirred reliably, and oxide films of the second abuttedportion J2 and of the overlapped surface between the stepped bottomsurface 17 a and the rear surface 3 b of the sealing body 3 are reliablyshut off. Therefore, joining strength of the second abutted portion J2is further increased.

Further, according to the method for manufacturing a liquid coolingjacket of the present embodiment, only the distal end pin F3 and thebase end pin F2 are inserted in the jacket body 2 and the sealing body3. Therefore, a load on the friction stirring apparatus is reduced morethan a case in which a shoulder portion of a rotary tool is pressed, andthe primary joining rotary tool F is operated more stably. Stillfurther, the load on the friction stirring apparatus is reduced so thatthe first abutted portion J1 and the second abutted portion J2 locatedin a deep position are joined without a large load on the frictionstirring apparatus.

Furthermore, according to the method for manufacturing a liquid coolingjacket of the present embodiment, the provisional joining step isperformed prior to the first primary joining step, and therefore whenthe first and second primary joining steps are performed, the firstabutted portion J1 and the second abutted portion J2 are each preventedfrom coming apart.

Further, in the present embodiment, the columnar supports 12 (columnarsupport end surfaces 16 a) are exposed to the front surface 3 a of thesealing body 3, to facilitate performing the hole-forming step to formthe fixing holes X and the mounting step to mount the heating element H.Still further, the columnar supports 12 are directly brought in contactwith the heating element H, to further improve cooling efficiency.

The method for manufacturing a liquid cooling jacket according to thefirst embodiment of the present invention is described above, but designcan be appropriately modified in a range without departing from thescope of the present invention. In the present embodiment, the primaryjoining step is performed in the order of the first abutted portion J1and the second abutted portions J2, but the second abutted portions J2may be firstly joined by friction stirring. Further, in the firstprimary joining step and the second primary joining step, friction stirjoining may be performed while the jacket body 2 and the sealing body 3are cooled by a cooling medium caused to flow inside the jacket body 2.Thus, frictional heat is kept low so that deformation of the liquidcooling jacket 1 due to thermal contraction is reduced. Still further,according to the method, joining can be made while the jacket body 2 andthe jacket body 3 themselves are cooled without separately using acooling plate, a cooling device, or the like.

Further, a planar cross-sectional shape of the columnar support 12 is acircular shape, but may be an ellipse shape or another polygonal shape.

Further, in the first embodiment, provisional joining is performed withthe provisional joining rotary tool G, but may be performed with theprimary joining rotary tool F. Thus, replacing the rotary tools can beeliminated. Still further, the provisional joining step may be performedto at least either one of the first abutted portion J1 and the secondabutted portion J2. Yet further, the provisional joining step may beperformed by welding.

[First Modification]

Next, a description is given of a method for manufacturing a liquidcooling jacket according to a first modification of the firstembodiment. As illustrated in FIG. 20, the first modification differsfrom the first embodiment in that the provisional joining step, thefirst primary joining step, and the second primary joining step areperformed with use of a cooling plate. The first modification isdescribed with a focus on structures different from the firstembodiment.

As illustrated in FIG. 20, in the first modification, the jacket body 2is fixed to a table K at the time of performing the fixing step. Thetable K includes a substrate K1 having a rectangular parallelepipedshape, clamps K3 formed at four corners of the substrate K1, and acooling pipe WP disposed within the substrate K1. The table K is amember which immovably fixes the jacket body 2 thereto and serves as a“cooling plate” set forth in claims.

The cooling pipe WP is a tubular member embedded inside the substrateK1. The cooling pipe WP is adapted to allow a cooling medium for coolingthe substrate K1 to flow therein. A location of the cooling pipe WP,that is, the shape of a cooling flow path allowing the cooling medium toflow therein, is not particularly limited, but in the firstmodification, is of a planar shape which follows the moving trace of theprimary joining rotary tool F in the first primary joining step. Morespecifically, the cooling pipe WP is disposed such that the cooling pipeWP and the first abutted portion J1 are approximately overlapped witheach other in planar view.

In the provisional joining step, the first primary joining step, and thesecond primary joining step in the first modification, the jacket body 2is first fixed to the table K and friction stir joining is thenperformed while allowing a cooling medium to flow in the cooling pipeWP. This allows frictional heat generated in the friction stirring to besuppressed low, thus deformation of the liquid cooling jacket 1 due toheat contraction is reduced. Further, in the first modification, sincethe cooling flow path is disposed to overlap with the first abuttedportion J1 (the moving traces of the provisional joining rotary tool Gand the primary joining rotary tool F) in planar view, a portion, inwhich the frictional heat is generated, is intensively cooled. Thisincreases cooling efficiency. Still further, the cooling pipe WP isdisposed to allow a cooling medium to flow therein, to facilitatecontrol of the cooling medium. Yet further, since the table K (coolingplate) and the jacket body 2 are brought in surface-contact with eachother, the cooling efficiency is further increased.

In addition to cooling of the jacket body 2 and the sealing body 3 withuse of the table K (cooling plate), the friction stir joining may beperformed while allowing a cooling medium to also flow within the jacketbody 2.

[Second Modification]

Next, a description is given of a method for manufacturing a liquidcooling jacket according to a second modification of the firstembodiment. As illustrated in FIGS. 21 and 22, the second modificationdiffers from the first embodiment in that the first primary joining stepand the second primary joining step are performed in a state where afront surface of the jacket body 2 and a front surface 3 a of thesealing body 3 are curved so as to have a convex shape. The secondmodification is described with a focus on structures different from thefirst embodiment.

As illustrated in FIG. 21, a table KA is employed in the secondmodification. The table KA includes a substrate KA1 having a rectangularparallelepiped shape, a spacer KA2 formed at the center of the substrateKA1, and clamps KA3 formed in four corners of the substrate KA1. Thespacer KA2 may be formed integrally with or separately from thesubstrate KA1.

In the fixing step of the second modification, the jacket body 2 and thesealing body 3 integrated with each other through the provisionaljoining step are fixed to the table KA with the clamps KA3. Asillustrated in FIG. 22, when fixed to the table KA, the jacket body 2and the sealing body 3 are curved so as to have the bottom portion 10and peripheral wall end surface 11 a of the jacket body 2, and the frontsurface 3 a of the sealing body 3 made to be convex upward. Morespecifically, the jacket body 2 is curved so as to have a first sideportion 21 of the wall portion 11A, a second side portion 22 of the wallportion 11B, a third side portion 23 of the wall portion 11C, and afourth side portion 24 of the wall portion 11D made to be curved lines.

In the first and second primary joining steps of the secondmodification, friction stir joining is performed with the primaryjoining rotary tool F. In the first and second primary joining steps, anamount of deformation of at least one of the jacket body 2 and thesealing body 3 is measured in advance and friction stir joining is thenperformed while the insertion depth of the distal end pin F3 of theprimary joining rotary tool F is adjusted in accordance with the amountof deformation. That is, the primary joining rotary tool F is moved soas to have the moving trace thereof made to be a curved line along thecurved surfaces of the peripheral wall end surface 11 a of the jacketbody 2 and the front surface 3 a of the sealing body 3. This makes thedepth and width of the plasticized regions W1 and W2 constant.

There is a risk that heat input due to friction stir joining causes heatcontraction to be generated in the plasticized regions W1 and W2 to havethe sealing body 3 of the liquid cooling jacket 1 deformed into aconcave shape. However, according to the first and second primaryjoining steps of the second modification, since the jacket body 2 andthe sealing body 3 are held in a convex shape in advance so that atensile stress acts on the peripheral wall end surface 11 a and thefront surface 3 a, the liquid cooling jacket 1 becomes flat by makinguse of heat contraction after friction stir joining. Further, in a casewhere the primary joining step is performed with the conventional rotarytool, when the jacket body 2 and the sealing body 3 are curved in aconvex shape, the shoulder portion of the rotary tool comes in contactwith the jacket body 2 and the sealing body 3 and thus the rotary toolis not suitably operated. However, according to the second modification,since the primary joining rotary tool F has no shoulder portion, theprimary joining rotary tool F is suitably operated even when the jacketbody 2 and the sealing body 3 are curved in a convex shape.

The amount of deformation of the jacket body 2 and the sealing body 3may be measured with use of a known height detecting device. Further,for example, a friction stirring apparatus, which is equipped with adetecting device to detect a height from the table KA to at least one ofthe jacket body 2 and the sealing body 3, may be used. The first andsecond primary joining steps may be performed while the amount ofdeformation of the jacket body 2 or the sealing body 3 is detected.

Further, although the jacket body 2 and the sealing body 3 are curved soas to have all of the first to fourth side portions 21 to 24 made to becurved lines in the second modification, the shape of curves is notlimited thereto. For example, the jacket body 2 and the sealing body 3may be curved so as to have the first side portion 21 and the secondside portion 22 made to be straight lines and the third side portion 23and the fourth side portion 24 made to be curved lines.

Still further, for example, the jacket body 2 and the sealing body 3 maybe curved so as to have the first side portion 21 and the second sideportion 22 made to be curved lines and the third side portion 23 and thefourth side portion 24 made to be straight lines.

Further, in the second modification, although the height position of thedistal end pin F3 of the primary joining rotary tool F is changed inaccordance with the amount of deformation of the jacket body 2 or thesealing body 3, the primary joining step may be performed with theheight of the distal end pin F3 of the primary joining rotary tool Frelative to the table KA being kept constant.

Further, the spacer KA2 may have any shape as long as the jacket body 2and the sealing body 3 can be fixed so as to have the front surfacesthereof made to be convex. Still further, the spacer KA2 may be omittedas long as the jacket body 2 and the sealing body 3 can be fixed so asto have the front surfaces thereof made to be convex. Yet further, theprimary joining rotary tool F may be attached to, for example, a robotarm including a spindle unit at a head thereof.

According to the structure, the rotation axes of the primary joiningrotary tool F is easily inclined at various angles.

[Third Modification]

Next, a description is given of a method for manufacturing a liquidcooling jacket according to a third modification of the firstembodiment. As illustrated in FIG. 23, the third modification differsfrom the first embodiment in that the jacket body 2 and the sealing body3 are formed in advance so as to be curved in a convex shape toward thefront surface side in the preparing step. The third modification isdescribed with a focus on structures different from the firstembodiment.

In the preparing step according to the third modification, the jacketbody 2 and the sealing body 3 are formed by die-casting so as to havethe front surfaces thereof to be curved into a convex shape. The jacketbody 2 is formed such that the bottom portion 10 and the peripheral wallportion 11 are formed in a convex shape toward the front surface,respectively. Further, the sealing body 3 is formed to have the frontsurface 3 a thereof in a convex shape.

As illustrated in FIG. 24, in the third modification, the jacket body 2and the sealing body 3 provisionally joined together are fixed to atable KB at the time of performing the fixing step. The table KBincludes a substrate KB1 in a rectangular parallelepiped shape, a spacerKB2 disposed at the center of the substrate KB1, clamps KB3 formed atfour corners of the substrate KB1, and a cooling pipe WP embedded insidethe substrate KB1. The table KB is a member which immovably fixes thejacket body 2 thereto and serves as a “cooling plate” set forth inclaims.

The spacer KB2 includes a curved surface KB2 a curved to have anupwardly convex shape, and upright surfaces KB2 b, KB2 b formed at bothends of the curved surface KB2 a and rising from the substrate KB1. Thespacer KB2 has a first side portion Ka and a second side portion Kb madeto be curved lines, and a third side portion Kc and a fourth sideportion Kd made to be straight lines.

The cooling pipe WP is a tubular member embedded inside the substrateKB1. The cooling pipe WP is adapted to allow a cooling medium forcooling the substrate KB1 to flow therein. A location of the coolingpipe WP, that is, a shape of a cooling flow path allowing the coolingmedium to flow therein, is not particularly limited, but in the thirdmodification, is of a planar shape to follow the moving trace of theprimary joining rotary tool F in the first primary joining step. Morespecifically, the cooling pipe WP is disposed such that the cooling pipeWP and the first abutted portion J1 are approximately overlapped witheach other in planar view.

In the fixing step of the third modification, the jacket body 2 and thesealing body 3 integrated with each other through the provisionaljoining step are fixed to the table KB with the clamps KB3. Morespecifically, the jacket body 2 and the sealing body 3 are fixed to thetable KB such that the rear surface of the bottom portion 10 of thejacket body 2 comes in surface-contact with the curved surface KB2 a.When the jacket body 2 is fixed to the table KB, the jacket body 2 iscurved such that the first side portion 21 of the wall portion 11Athereof and the second side portion 22 of the wall portion 11B thereofare made to be curved lines, and the third side portion 23 of the wallportion 11C thereof and the fourth side portion 24 of the wall portion11D thereof are made to be straight lines.

In the first and second primary joining steps of the third modification,friction stir joining is performed for the first abutted portion J1 andthe second abutted portion J2, respectively, with the primary joiningrotary tool F. In the first and second primary joining steps, the amountof deformation of at least one of the jacket body 2 and the sealing body3 is measured in advance and the friction stir joining is then performedwhile the insertion depth of the distal end pin F3 of the primaryjoining rotary tool F is adjusted in accordance with the amount ofdeformation. That is, the primary joining rotary tool F is moved so asto have the moving trace thereof made to be a curved line or a straightline along the peripheral wall end surface 11 a of the jacket body 2 andthe front surface 3 a of the sealing body 3. This makes the depth andwidth of the plasticized region W1 constant.

There is a risk that heat input due to friction stir joining causes heatcontraction to be generated in the plasticized regions W1 and W2 to havethe sealing body 3 of the liquid cooling jacket 1 deformed into aconcave shape. However, according to the first and second primaryjoining steps of the third modification, since the jacket body 2 and thesealing body 3 are formed in a convex shape in advance, the liquidcooling jacket 1 becomes flat by making use of heat contraction afterfriction stir joining.

Further, in the third modification, the curved surface KB2 a of thespacer KB2 is made to come in surface-contact with the rear surface in aconcave shape of the bottom portion 10 of the jacket body 2. With thestructure, friction stir joining is performed while the jacket body 2and the sealing body 3 are cooled more effectively. Since the frictionalheat generated in the friction stir joining is suppressed low,deformation of the liquid cooling jacket 1 due to heat contraction isreduced. This allows the jacket body 2 and the sealing body 3 to have areduced curvature when the jacket body 2 and the sealing body 3 areformed into a convex shape in the preparing step.

The amount of deformation of the jacket body 2 and the sealing body 3may be measured with use of a known height detecting device. Further,for example, a friction stirring apparatus, which is equipped with adetecting device to detect a height from the table KB to at least one ofthe jacket body 2 and the sealing body 3, may be used. The primaryjoining step may be performed while the amount of deformation of thejacket body 2 or the sealing body 3 is detected.

Further, although the jacket body 2 and the sealing body 3 are curved soas to have the first side portion 21 and the second side portion 22 madeto be curved lines in the third modification, the shape of curves is notlimited thereto. For example, the spacer KB2 having a spherical surfacemay be formed so that the rear surface of the bottom portion 10 of thejacket body 2 is made to come in surface-contact with the sphericalsurface. In this case, when the jacket body 2 is fixed to the table KB,all of the first to fourth side portions 21 to 24 are made to be curvedlines.

Further, in the third modification, although the height position of thedistal end pin F3 of the primary joining rotary tool F is changed inaccordance with the amount of deformation of the jacket body 2 or thesealing body 3, the primary joining step may be performed with theheight of the distal end pin F3 of the primary joining rotary tool Frelative to the table KB being kept constant.

Second Embodiment

Next, a description is given of a method for manufacturing a liquidcooling jacket according to a second embodiment of the presentinvention. As illustrated in FIG. 25, the second embodiment differs fromthe first embodiment in that a columnar support 12 does not have acolumnar support stepped portion thereon. The method for manufacturing aliquid cooling jacket according to the second embodiment is describedwith a focus on structures different from the first embodiment.

A liquid cooling jacket 1A according to the second embodiment includes ajacket body 2A and a sealing body 3A. The jacket body 2A is a box-shapedbody whose top is open. The jacket body 2A includes a bottom portion 10,a peripheral wall portion 11, and a plurality of columnar supports 12. Amaterial of the jacket body 2A is appropriately selected fromfrictionally stirrable metal such as aluminum, an aluminum alloy,copper, a copper alloy, titanium, a titanium alloy, magnesium, and amagnesium alloy. In the present embodiment, the jacket body 2A is madeof an aluminum alloy which is the same material as the sealing body 3A,but an aluminum alloy casting material (such as JIS AC4C, ADC12) may beused. The bottom portion 10 has a rectangular shape in planar view. Theperipheral wall portion 11 includes wall portions 11A, 11B, 11C, and11D, each having the same plate thickness.

A peripheral wall stepped portion 14 is formed at the peripheral wallend surface 11 a of the peripheral wall portion 11 along a peripheraledge of the opening of the jacket body 2A. The peripheral wall steppedportion 14 includes a stepped bottom surface 14 a and a stepped sidesurface 14 b rising from the stepped bottom surface 14 a. The steppedbottom surface 14 a is formed at a position one step lower than theperipheral wall end surface 11 a.

The columnar supports 12 are provided to stand on the bottom portion 10and have a columnar shape. The number of the columnar supports 12 is notlimited as long as one or more columnar supports are arranged, and fourcolumnar supports are arranged in the present embodiment. The columnarsupports 12 each have the same shape. A columnar support end surface 12a as an end surface of the columnar support 12 is formed to have thesame height as the stepped bottom surface 14 a of the peripheral wallstepped portion 14.

The sealing body 3A is a plate-shaped member having a rectangular shapein planar view. In the present embodiment, the sealing body 3A is madeof an aluminum alloy which is the same material as that of the jacketbody 2A, but an aluminum wrought alloy material (such as JIS A1050,A1100, and A6063) may be used. The sealing body 3A is formed to have asize to be placed on the peripheral wall stepped portion 14 without anygap. The sealing body 3A has approximately the same thickness as theheight of the stepped side surface 14 b.

As illustrated in FIG. 26, the liquid cooling jacket 1A is formed of thejacket body 2A and the sealing body 3A being integrally joined togetherby friction stirring. The liquid cooling jacket 1A is joined by frictionstirring, respectively, at the first abutted portion J1 where thestepped side surface 14 b (see FIG. 25) of the peripheral wall steppedportion 14 is abutted with the outer peripheral side surface 3 c of thesealing body 3A and at four overlapped portions J3 where the rearsurface 3 b of the sealing body 3A are overlapped with the columnarsupport end surfaces 12 a of the columnar supports 12. The plasticizedregion W1 is formed at the first abutted portion J1, and the plasticizedregions W2 are formed at the overlapped portions J3. The liquid coolingjacket 1A has a hollow portion formed therein, in which heat transportfluid flows for transporting heat outside.

Next, a description is given of a method for manufacturing a liquidcooling jacket (a method for manufacturing a liquid cooling jackethaving a heating element) according to the second embodiment. The methodfor manufacturing a liquid cooling jacket includes a preparing step, aplacing step, a fixing step, a provisional joining step, a first primaryjoining step, a second primary joining step, a hole-forming step, a burrremoving step, and a mounting step.

As illustrated in FIG. 25, the preparing step is a step of forming thejacket body 2A and the sealing body 3A. The jacket body 2A is formed bydie-casting, for example.

As illustrated in FIGS. 27 and 28, the placing step is a step of placingthe sealing body 3A in the jacket body 2A. The rear surface 3 b of thesealing body 3A is brought in surface-contact with the stepped bottomsurface 14 a of the peripheral wall stepped portion 14 and the columnarsupport end surfaces 12 a of the columnar supports 12, respectively. Theplacing step makes the stepped side surface 14 b of the peripheral wallstepped portion 14 abutted with the outer peripheral side surface 3 c ofthe sealing body 3A to form the first abutted portion J1. The firstabutted portion J1 has a rectangular shape in planar view. Further, theplacing step makes the rear surface 3 b of the sealing body 3Aoverlapped with the columnar support end surfaces 12 a of the columnarsupports 12 to form the overlapped portions J3. The overlapped portionJ3 has a circular shape in planar view.

In the fixing step, the jacket body 2A is fixed to a table (not shown).The jacket body 2A is immovably fixed to the table with fixing jigs suchas clamps.

As illustrated in FIG. 29, the provisional joining step is a step ofprovisionally joining the jacket body 2A to the sealing body 3A. Theprovisional joining step is the same as that in the first embodiment,and thus a description thereof is omitted.

As illustrated in FIGS. 30 and 31, the first primary joining step is astep of performing friction stir joining to the first abutted portion J1with the primary joining rotary tool F. The first primary joining stepis the same as that in the first embodiment, and thus a descriptionthereof is omitted.

As illustrated in FIGS. 32 and 33, the second primary joining step is astep of performing friction stir joining to the respective overlappedportions J3 with the primary joining rotary tool F. In the secondprimary joining step, the primary joining rotary tool F rotatedclockwise is inserted from the front surface 3 a of the sealing body 3Ainto the start position s2. Then, the primary joining rotary tool F isrelatively moved counterclockwise in the outer peripheral edge of thecolumnar support 12. The plasticized regions W2 are formed in theoverlapped portions J3 through the second primary joining step.

As illustrated in FIG. 33, in the second primary joining step, frictionstir joining is performed in a state where the sealing body 3A isbrought in contact with the distal end pin F3 and the sealing body 3A isbrought in contact with the base end pin F2. In the second primaryjoining step, friction stir joining is performed while the front surface3 a of the sealing body 3A is pressed by the outer peripheral surface ofthe base end pin F2 of the primary joining rotary tool F. Further, theinsertion depth of the primary joining rotary tool F is set such thatthe flat surface F4 of the distal end pin F3 comes in contact with onlythe sealing body 3 and the distal end surface F6 of the protrusion F5comes in contact with the columnar support 12. Metal around theprotrusion F5 is brought upward by the protrusion F5 and is pressed bythe flat surface F4. Thus, a vicinity of the protrusion F5 isfrictionally stirred reliably, and an oxide film of the overlappedportion J3 is reliably shut off. Therefore, joining strength of theoverlapped portion J3 is further increased.

The insertion depth of the primary joining rotary tool F is notnecessarily constant. The insertion depth may be changed between thefirst primary joining step and the second primary joining step, forexample.

In the second primary joining step, when the primary joining rotary toolF is moved counterclockwise with respect to the columnar support 12 asin the present embodiment, the primary joining rotary tool F ispreferably rotated clockwise. Meanwhile, when the primary joining rotarytool F is moved clockwise with respect to the columnar support 12, theprimary joining rotary tool F is preferably rotated counterclockwise. Bysetting the traveling direction and rotating direction of the primaryjoining rotary tool F as described above, even if joint defects aregenerated due to friction stir joining, the defects are generated on thecolumnar support 12 side having a relatively large thickness which isfar away from the hollow portion of the liquid cooling jacket 1A so thatthe degradation in watertightness and airtightness is reduced.

As illustrated in FIG. 32, the primary joining rotary tool F is movedaround by one lap in the overlapped portion J3 and then continuouslymoved to pass through a start position s2. Then, the primary joiningrotary tool F is moved to an end position e2 set on the sealing body 3A,and when reaching the end position e2, the primary joining rotary tool Fis moved upward so as to be pulled out of the sealing body 3A.

If a pulled-out mark remains in the sealing body 3A after the primaryjoining rotary tool F is pulled out of the overlapped portion J3, arepairing step of repairing the pulled-out mark may be performed. In therepairing step, the pulled-out mark is repaired by build-up welding tofill welded metal in the pulled-out mark, for example. Thus, the frontsurface 3 a of the sealing body 3A is flattened.

When the primary joining rotary tool F is pulled out of the sealing body3A, the primary joining rotary tool F may be shifted toward the centerof the columnar support 12 and then pulled out of the sealing body 3A.Further, when the primary joining rotary tool F is pulled out of thesealing body 3A, the primary joining rotary tool F may gradually bemoved upward while the primary joining rotary tool F is moved on thesealing body 3A, for example, so that the insertion depth of the primaryjoining rotary tool F is gradually shallower. Thus, a pulled-out markafter the second primary joining step does not remain or is made smalleron the sealing body 3A.

As illustrated in FIG. 34, the hole-forming step is a step of formingfixing holes X which communicate with the sealing body 3A and thecolumnar supports 12 and are used to fix a heating element H. The fixingholes X are each formed to penetrate a part of the plasticized region W2so as to reach the columnar support 12.

The burr removing step is a step of removing burrs which are exposed onthe front surfaces of the jacket body 2 and the sealing body 3A throughthe first primary joining step, the second primary joining step, and thehole-forming step. With the step, the front surfaces of the jacket body2 and the sealing body 3A are clearly finished.

As illustrated in FIG. 35, the mounting step is a step of mounting theheating element H with fitting members M. When the heating element H ismounted, through holes formed in a flange H1 of the heating element Hare communicated with the fixing holes X and the heating element H isfixed with the fitting members M such as screws. The fitting members Mare each inserted to a position reaching the columnar support 12.

In the present embodiment, the fixing holes X are formed in the sealingbody 3A side to have the heating element H fixed to the sealing body 3A,but the fixing holes X, which communicate with the bottom portion 10 andthe columnar supports 12, may be formed in the bottom portion 10 to havethe heating element H fixed to the bottom portion 10. The heatingelement H merely needs to be mounted to at least one of the sealing body3A and the bottom portion 10. Further, in the present embodiment, thefixing holes X are formed, but the heating element H may be fixed withthe fitting members M without the fixing holes X being formed.

The method for manufacturing a liquid cooling jacket as described abovealso achieves substantially the same effects as the first embodiment. Inthe first embodiment, the second abutted portions J2 (see FIG. 12) areexposed to the sealing body 3, but, in the second embodiment, theabutted portions are not exposed. However, as described in the secondembodiment, the overlapped portions J3 are frictionally stirred fromabove the sealing body 3 so that the sealing body 3 is joined to thecolumnar supports 12. Further, in the second embodiment, since thesealing body 3A does not have hole portions and a columnar supportstepped portion is not formed in the columnar support 12, the liquidcooling jacket is easily manufactured.

Further, according to the method for manufacturing a liquid coolingjacket of the present embodiment, the base end pin F2 and the distal endpin F3 are inserted in the sealing body 3. Therefore, a load on thefriction stirring apparatus is reduced more than a case in which ashoulder portion of a rotary tool is pressed, and the primary joiningrotary tool F is operated more stably. Still further, the load on thefriction stirring apparatus is reduced so that the first abutted portionJ1 located in a deep position is joined without a large load on thefriction stirring apparatus.

Further, in the second primary joining step, friction stirring isperformed to the inner side of the outer peripheral edge of the columnarsupport 12 therearound by one lap or more as in the present embodimentso that watertightness and airtightness are improved. The moving routeof the primary joining rotary tool F in the second primary joining stepis not necessarily one lap or more. The moving route may be set suchthat the plastically fluidized material does not flow inside the liquidcooling jacket 1A and at least a portion of the overlapped portion J3may be subjected to friction stir joining.

The second embodiment of the present invention is described above, butdesign can be appropriately modified in a range without departing fromthe scope of the present invention.

For example, in the second embodiment, the manufacturing method ofeither one of the first to third modifications described above may beemployed to manufacture the liquid cooling jacket 1A.

The embodiments and the modifications of the present invention aredescribed above, and the design can be appropriately modified. Forexample, fins may be arranged on at least one of the jacket body and thesealing body. Further, in the first primary joining step, the primaryjoining rotary tool F may be moved by two laps in the first abuttedportion J1. Still further, different rotary tools may be used betweenthe first primary joining step and the second primary joining step. Yetfurther, in each embodiment, the present invention is applied to amethod for manufacturing a liquid cooling jacket with the heatingelement H, but can also be applied to a method for manufacturing aliquid cooling jacket without the heating element H. In this case, thehole-forming step and the mounting step are omitted.

Design of the primary joining rotary tool F of the present invention canbe appropriately modified. FIG. 36 is a side view of a firstmodification of the primary joining rotary tool of the presentinvention. As illustrated in FIG. 36, a primary joining rotary tool Faaccording to the first modification has a stepped angle C1 of 85°defined by the stepped bottom surface 30 a and stepped side surface 30 bof the pin stepped portion 30. The stepped bottom surface 30 a isparallel to the horizontal plane. Thus, the stepped bottom surface 30 ais parallel to the horizontal plane, to have the stepped angle C1 set toan acute angle to such an extent that a plastically fluidized materialflows outside without accumulating in and adhering to the pin steppedportion 30 during friction stirring.

FIG. 37 is a side view of a second modification of the primary joiningrotary tool of the present invention. As illustrated in FIG. 37, aprimary joining rotary tool Fb according to the second modification hasa stepped angle C1 of 115° at the pin stepped portion 30. The steppedbottom surface 30 a is parallel to the horizontal plane. Thus, thestepped bottom surface 30 a is parallel to the horizontal plane, to havethe stepped angle C1 set to an obtuse angle to such an extent as toserve as the pin stepped portion 30.

FIG. 38 is a side view of a third modification of the primary joiningrotary tool of the present invention. As illustrated in FIG. 38, in aprimary joining rotary tool Fc according to the third modification, thestepped bottom surface 30 a is inclined upward at an angle of 10° withrespect to the horizontal plane from the rotation axis of the tooltoward the outer direction. The stepped side surface 30 b is parallel tothe vertical plane. Thus, the stepped bottom surface 30 a may be formedto be inclined upward with respect to the horizontal surface from therotation axis of the tool toward the outer direction to such an extentthat a plastically fluidized material is pressed during frictionstirring. The primary joining rotary tool described above in the firstto third modifications achieves the same effects as the presentembodiment.

REFERENCE NUMERALS

1 liquid cooling jacket

1A liquid cooling jacket

2 jacket body

2A jacket body

3 sealing body

3A sealing body

3 a front surface

3 b rear surface

3 c outer peripheral side surface

10 bottom portion

11 peripheral wall portion

11A wall portion

11B wall portion

11C wall portion

11D wall portion

11 a peripheral wall end surface

12 columnar support

12 a columnar support end surface

13 recessed portion

14 peripheral wall stepped portion

14 a stepped bottom surface

14 b stepped side surface

16 a columnar support end surface

17 columnar support stepped portion

17 a stepped bottom surface

17 b stepped side surface

F primary joining rotary tool (rotary tool)

Fa primary joining rotary tool

Fb primary joining rotary tool

Fc primary joining rotary tool

F1 base shaft portion

F2 base end pin

F3 distal end pin

30 pin stepped portion

30 a stepped bottom surface

30 b stepped side surface

31 spiral groove

A1 taper angle (of base end pin)

A2 taper angle

C1 stepped angle

C2 spiral angle

Z1 distance (of base end pin)

Z2 distance

Y1 height (of stepped side surface)

Y2 height

G provisional joining rotary tool

J1 first abutted portion

J2 second abutted portion

J3 overlapped portion

K table (cooling plate)

M fitting member

W1 plasticized region

W2 plasticized region

WP cooling pipe

1. A method for manufacturing a liquid cooling jacket, the liquidcooling jacket including a jacket body and a sealing body, the jacketbody including a bottom portion, a peripheral wall portion rising from aperipheral edge of the bottom portion, and a columnar support risingfrom the bottom portion, the sealing body having a hole portion intowhich a distal end of the columnar support is inserted, and sealing anopening of the jacket body, the jacket body being joined to the sealingbody by friction stirring, the method comprising steps of: preparing forforming a peripheral wall stepped portion including a stepped bottomsurface and a stepped side surface rising from the stepped bottomsurface on an inner peripheral edge of the peripheral wall portion,forming a columnar support end surface of the columnar support so as tohave the same height as a peripheral wall end surface of the peripheralwall portion, and forming a columnar support stepped portion including astepped bottom surface and a stepped side surface rising from thestepped bottom surface on an outer periphery of a distal end of thecolumnar support; placing the sealing body in the jacket body; firstprimary joining of performing friction stirring to a first abuttedportion, where the stepped side surface of the peripheral wall steppedportion is abutted with an outer peripheral side surface of the sealingbody, with a rotary tool being moved around the first abutted portion byone lap; and second primary joining of performing friction stirring to asecond abutted portion, where the stepped side surface of the columnarsupport stepped portion is abutted with a hole wall of the hole portion,with a rotary tool being moved around the second abutted portion by onelap, wherein the rotary tool is a primary joining rotary tool forfriction stirring to include a base end pin and a distal end pin,wherein a taper angle of the base end pin is larger than a taper angleof the distal end pin, the base end pin includes a pin stepped portionin a stepped shape formed on an outer peripheral surface thereof, andthe distal end pin includes a flat surface perpendicular to a rotationaxis of the rotary tool and includes a protrusion protruding from theflat surface, and wherein, in the first primary joining and the secondprimary joining, the friction stirring is performed in a state where thejacket body and the sealing body are brought in contact with the flatsurface of the distal end pin and the base end pin, and only the jacketbody is brought in contact with a distal end surface of the protrusion.2. A method for manufacturing a liquid cooling jacket, the liquidcooling jacket including a jacket body and a sealing body, the jacketbody including a bottom portion, a peripheral wall portion rising from aperipheral edge of the bottom portion, and a columnar support risingfrom the bottom portion, the sealing body sealing an opening of thejacket body, the jacket body being joined to the sealing body byfriction stirring, the method comprising steps of: preparing for forminga peripheral wall stepped portion including a stepped bottom surface anda stepped side surface rising from the stepped bottom surface on aninner peripheral edge of the peripheral wall portion, and forming acolumnar support end surface of the columnar support so as to have thesame height as the stepped bottom surface of the peripheral wall steppedportion; placing the sealing body in the jacket body; first primaryjoining of performing friction stirring to a first abutted portion,where the stepped side surface of the peripheral wall stepped portion isabutted with an outer peripheral side surface of the sealing body, witha rotary tool being moved around the first abutted portion by one lap;and second primary joining of performing friction stirring to anoverlapped portion, where the columnar support end surface of thecolumnar support is overlapped with a rear surface of the sealing body,with a rotary tool being moved around the overlapped portion, whereinthe rotary tool is a primary joining rotary tool for friction stirringto include a base end pin and a distal end pin, wherein a taper angle ofthe base end pin is larger than a taper angle of the distal end pin, thebase end pin includes a pin stepped portion in a stepped shape formed onan outer peripheral surface thereof, and the distal end pin includes aflat surface perpendicular to a rotation axis of the rotary tool andincludes a protrusion protruding from the flat surface, and wherein, inthe first primary joining, the friction stirring is performed in a statewhere the jacket body and the sealing body are brought in contact withthe flat surface of the distal end pin and the base end pin, and onlythe jacket body is brought in contact with a distal end surface of theprotrusion, and in the second primary joining, the friction stirring isperformed in a state where the sealing body is brought in contact withthe flat surface of the distal end pin and the base end pin, and thejacket body is brought in contact with the distal end surface of theprotrusion.
 3. The method for manufacturing a liquid cooling jacket asclaimed in claim 1, wherein, in the preparing, the jacket body is formedby die-casting to have the bottom portion formed to be convex toward afront surface of the jacket body, and the sealing body is formed to beconvex toward a front surface thereof
 4. The method for manufacturing aliquid cooling jacket as claimed in claim 3, wherein an amount ofdeformation of the jacket body is measured in advance, and in the firstprimary joining and the second primary joining, the friction stirring isperformed while an insertion depth of the rotary tool is adjusted inaccordance with the amount of deformation.
 5. The method formanufacturing a liquid cooling jacket as claimed in claim 1, furthercomprising provisional joining of provisionally joining at least eitherone of the first abutted portion and the second abutted portion prior tothe first primary joining and the second primary joining.
 6. The methodfor manufacturing a liquid cooling jacket as claimed in claim 2, furthercomprising provisional joining of provisionally joining the firstabutted portion prior to the first primary joining.
 7. The method formanufacturing a liquid cooling jacket as claimed in claim 1, wherein, inthe first primary joining and the second primary joining, a coolingplate, in which a cooling medium flows, is arranged to face a rearsurface of the bottom portion, and the friction stirring is performedwhile the jacket body and the sealing body are cooled by the coolingplate.
 8. The method for manufacturing a liquid cooling jacket asclaimed in claim 7, wherein a front surface of the cooling plate isbrought in surface-contact with a rear surface of the bottom portion. 9.The method for manufacturing a liquid cooling jacket as claimed in claim7, wherein the cooling plate has a cooling flow path in which thecooling medium flows, and wherein the cooling flow path has a planarshape to follow a moving trace of the rotary tool in the first primaryjoining.
 10. The method for manufacturing a liquid cooling jacket asclaimed in claim 7, wherein the cooling flow path, in which the coolingmedium flows, is formed of a cooling pipe embedded in the cooling plate.11. The method for manufacturing a liquid cooling jacket as claimed inclaim 1, wherein, in the first primary joining and the second primaryjoining, a cooling medium flows in a hollow portion defined by thejacket body and the sealing body, and the friction stirring is performedwhile the jacket body and the sealing body are cooled.